Leaves of the plant camellia sinensis have long been used in order to make beverages known as “tea”. A variety of specific teas have been produced from this plant, such as white tea, green tea, oolong tea, and black tea, each depending on the type and degree of post harvest processing to which the leaves are subjected. For example, the preparation of leaves for white and green teas include only the steaming and drying of leaf and bud. By contrast, leaves used to make oolong and black teas are typically withered, steamed and then fermented or oxidized to a selected degree. Of these, green tea and white tea are the least processed, black tea leaves are the most processed, and oolong tea leaves receive an intermediate degree of processing. Once the tea leaves have been prepared, the basic process of making a tea beverage typically entails brewing, steeping, or infusing the prepared leaves in hot water.
While tea has been traditionally prepared and consumed as a hot aqueous infusion or brew for several centuries, modern times have produced a number of variations on this known standard. Iced tea prepared and served cold, instant tea produced from a fully soluble powder, and bottled tea prepared and shipped in a liquid state have all found a consumer demand. Moreover, a number of additional herbal ingredients have now been included with the tea in order to provide specifically desired positive health benefits.
Of course, such preparations typically require a complicated production procedure and often require the use of various chemicals and additives. For example, U.S. Pat. No. 6,482,450 to Goodsall et al., which is incorporated herein by reference, discloses methods for producing a black leaf tea that infuses in either hot or cold water. The basic process described entails treating macerated green tea leaves with tannase, and then fermenting in the presence of a sufficient amount hydrogen peroxide to activate endogenous peroxidases and oxidize gallic acid and other tannase-liberated elements. The mixture is then dried.
In addition to traditional and cultural reasons for consuming tea, a renewed interest has been fueled by the discovery of strong antioxidant properties provided by tea prepared from camellia sinensis leaves. Such an antioxidant effect has been primarily attributed to the polyphenol content of the tea leaves.
The active constituents of green tea are believed to be the polyphenols, commonly known as tea catechins. The major tea catechins are epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC). Of these, EGCG is the most abundant and possesses the most potent antioxidative activity. Various polyphenols are thought to provide an antioxidant effect that may treat or prevent various forms of cancer, and may also treat or prevent other chronic diseases, such as atherosclerosis. See, Zhao B. et al., Cell Biophys. 14, 175 (1989); and Huang M. T. et al., Carcinogenesis 13, 947 (1992); Nakachi K, Eguchi H, Imai K., Ageing Res Rev. January 2003, 2(1): 1-10.; Katiyar S K., Curr Drug Targets Immune Endocr Metabol Disord. 2003 September; 3(3): 234-42; Adhami V M, Ahmad N, Mukhtar H., J. Nutr. 2003July; 133(7 Suppl): 2417S-2424S; Maron D J, et al. Arch Intern Med. 2003 Jun. 23; 163(12): 1448-53; Raederstorff D G, Schlachter M F, Elste V, Weber P., J. Nutr Biochem. 2003June; 14(6):326-332; Roy M, Chakrabarty S, Sinha D, Bhattacharya R K, Siddiqi M, Mutat Res. 2003 February, 523-524:33-41; and Pan T. Jankovic J, Le W., Drugs Aging. 2003; 20(10): 711-21. Therefore, a number of processes for the preparation of tea extracts having improved or enhanced polyphenol potency have been sought.
Most methods for producing tea or green tea extracts with enhanced polyphenol potency require elevated temperatures during the extraction process and/or the use of specialized chemicals or organic solvents. For example, U.S. Pat. No. 4,613,672 to Hara, which is incorporated herein by reference, discloses processes for the production of tea catechins. Specific catechins, such as epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate may be produced by extracting tea leaves with hot water or an aqueous solution of methanol, ethanol, or acetone, washing the extract containing solution with chloroform, transferring the washed solution into an organic solvent, removing the solution and then passing it through a reversed phase column in the presence of an eluting solution. Additionally, U.S. Pat. No. 5,989,557, to Bombardelli et al. which is incorporated herein by reference, discloses an elaborate multi-step method for preparation of novel polyphenol fractions of camellia sinensis which requires a number of organic solvents and several phase separations.
While such methods may be effective for their respective purposes, they each require the use of one or more organic solvents or chemical substances that are not generally fit for human consumption in an appreciable amount. Further, such extraction processes may require heating or other processing conditions and equipment that can be of significant expense and can adversely impact the color, flavor, and organoleptic properties of the resulting tea product.
As a result, methods of preparing camellia sinensis extracts that have good natural color, robust natural flavor, and pleasant organoleptic properties, which also is high in polyphenol content, and does not require heating or organic solvents, or chemicals, and products made therefrom having such properties continue to be sought.